The ability to control one or more devices in a building (e.g., lighting, heating, air conditioning, security systems) based on one or more parameters (e.g., time, temperature, user preference) is known as building automation. Building automation may be implemented in any of a number of different types of buildings, including homes, offices, restaurants, stores, theaters, and hotels, to name only a few examples.
Building automation systems operate by issuing commands from a control panel (e.g., a keypad) to an output device (e.g., a lamp control). Inexpensive building automation systems are available which use the existing electrical wiring in the building for issuing commands to the output device. The control panel and output device are each plugged into electrical outlets in the home and the control panel issues commands via the electrical wiring in the home. However, the commands may be distorted or lost due to “noise” in the electrical wiring. In addition, such systems are limited to relatively few output devices.
Inexpensive building automation systems are also available in which the control panel issues radio frequency (RF) commands to the output devices. However, RF transmission is typically limited in range (e.g., by government regulation) and is subject to interference (e.g., from other RF devices).
Other building automation systems are available which implement RS232 architecture to issue commands from the control panel to the output devices. The RS232 architecture allows more reliable data exchange between the control panel and the output devices. However, the control panel (e.g., keypad) must be directly connected to each of the output devices (i.e., a point-to-point or so-called “hub-and-spoke” arrangement). Such an arrangement can only be used for short runs and is wiring intensive, making these systems expensive to install and maintain. In addition, the RS232 architecture does not provide for error-handling.